650 pistons in a 550 engine?

Does anyone know the key differences in the 650/550 engines? I know the transmission and the output are different but is there a difference in the valve train and the crankshaft?

I have a 50,000km 550 engine at home and I'm currently taking a machining course, I'm wondering, for one of my projects, if I could take the head/cylinders off the worn out engine and bore to fit a set of 650 pistons and do some porting.

It'll be a lot of work I know.
But how cool would a 650 Chain Drive 6 Speed be?!?!

Any input is appreciated

Thanks!

 

You'll sink A LOT of wasted money into that, along with a lot of wasted work

 

I don't think it will be that bad. a set of pistons will be around $150 max. Crank is about $70 (if needed). I'll have to track down (crank bearings again if needed). A Valvetrain if needed is going to run me about $250. Machining will all be very cheap if not free because I will be doing the bore in school. if the skirts won't allow a bore a new cylinder set is $160 used. Considering I bought the whole bike for $200 and this engine is my second (scrap) engine I wouldn't mind experimenting

 

Whatever you say, Boss---

Just seems to me that to try and bore the cyls from 57mm to 63mm is waaaaay over-bored. But, that's just me.....

Why not build off of an fz600, or radian 600 instead? They're basically a 550 that's been souped up......

 

I was told 61mm was the max you could go to or the 550 liner got too thin, maybe if you started with a 600 barrel it might give you a bit more leeway

 

The fz600 bore is 58.5, fwtw

 

a little education is a dangerous thing....
ask your shop teacher and he will tell you no way

we did have a member who was talking about the fz600 piston swap into a 550
do not know where he got

 

Wayyy overbored.
The cost won't come from the parts, but from the blowed-up engine.

You want more power, and want to spend money to get it.
Lower compression. Turbo (or supercharger). Cable-operated carbs. Done.

 

Going way back to my teenage days, I had a Cushman and had it bored out to the factory stated max. Man, it had compression and ran like a champ--for two weeks until it literally pulled the head away form the cylinder due to the thinness of the cylinder wall. I had to buy a new block and had it bored the minimum amount needed to clean it up and it was running when I left for college. A Cushman engine is a heck of a lot easier to work on than an XJ.

 

I've done that one, takes it up near the 550cc they are meant to be

The only way I could see it being done would be to remove the original liners and bore the block to suit the 650 liner (if there's enough meat between the cylinders)

 

Are you sure your engine is worn out?
I have 56k miles on my 550 and it is nowhere near worn out.

So,if you want to use this engine: service it and ride with it.
If you want more power, get antoher motorcycle

 

exactly

 

[QUOTE="Riley, post: 538156, member: 17863]

I have a 50,000km 550 engine......[/QUOTE]
I hadn't caught this part before----,that's barely over 31,000 mi. Not even tired enough to yawn. Get the valves back in spec, take the carbs to church, and you'll have more power and snot than you can handle.

 

you could put seca 550 cams in it and rejet carbs to seca carb specsor get seca carbs. this will make a differance in performance
follow that up with a taller rear tire for higher top end. you could go with seca rims (higher top end)and possibly tall tire if there is room (more top end)
taller tire ups top end and lowers rpm at highway speed

but as @hogfiddles stated " Get the valves back in spec, take the carbs to church, and you'll have more power and snot than you can handle."
doing this will give you more bang for your buck and you can save the money for a bigger bike if you are unhappy with the 550.

 

Sounds like an interesting project! Make sure you document every detail about it!
Your going to have a whole lot of researching, measuring, comparing, and calculating to do long before you will ever be ready to start thinking about any machining.
You will want to pick up the 650 parts to have on hand for measuring/comparing. Do not even begin to think that you can take some information from a web page and have everything magically line up.

A couple specs to get you started:
XJ550
Bore x Stroke: 57 x 51.8mm

XJ650
Bore x Stroke: 63 x 52.4mm (0.6mm increase in stroke)

FJ/XJ600
Bore x Stroke: 58.5 x 55.7mm

550 big bore: (645.89 CCs)
Bore x Stroke: 63 x 52.4mm


Starting with the obvious. The 6mm increase in the bore will never work with the stock 550 liners. You will have to install bigger liners.

From Xj4ever:
HCP12440SET4 Aftermarket standard-bore CYLINDER LINERS, set of 4: $ 309.95
HCP5541SET4 OEM cast aluminum bare PISTONS, for all XJ650 (except Turbo) engines, standard size, set of 4: $ 409.95
HCP5581SET4 OEM complete PISTON RING SETS, for all XJ650 engines, standard size, 4 complete sets:n $ 269.95
HCP5611 OEM machined PISTON PIN, for all XJ650, XJ700 non-X, and XJ750 engines, each: $ 29.95 (QTY 4: $ 119.80)
HCP5613 OEM machined piston pin CIRCLIP, for all XJ650, XJ700 non-X, XJ750 non-X, and all XJ900RK, RL, N/FN, and F engines, use 2 per piston, each: $ 2.50 (QTY 8: $ 20.00)
Total at time of posting: $ 1129.65 not including tax , or shipping.
Used parts will help reduce this drastically!

Note: This does not even begin to address the large amount of details that will need to be checked.
Bore Centers
Connecting Rods
Deck height
Valve Clearance

Just to name a few!

Based on experience and limited information this looks like a common sleeve and piston mod.
To give you a little reference so you know what you can expect: http://forums.sohc4.net/index.php?topic=40414.0

I have to go against the purist grain on this one and say that it does look like a possibility.
More info and research is required.
Count me on board!

Get that lump torn down and start measuring!

~Ghost

 

Oh it's a possibility, it's just a bit more work than I'd prefer do for the relatively small gain.

 

It'd be a sweet engine though. I wonder if you'd need to add much weight to the crank webs to balance the extra mass of the pisons. The single that I bored out by about that much was a shaker afterwords, and I used a slipper piston to try to keep the mass down as much as possible (didn't touch the crank).

 

HAHA!
Thanks for the replies guys! I unsubscribed to the emails and forgot I even posted this. and I come from a Snowmobile industry where 25,000 km on a 4 stroke sled basically means its trash, thats why I'm scared of 55k. guess Im going to tear that parts engine down and see what all is wrong with it (Cylinder 4 was not firing. made black soot and thats it). It was the original engine to my bike and my second engine won't pass a safety as it leaks oil. I guess Ill be trying to see if I can get it to work as a stock engine and if that doesn't work out it'll be a Frankenstein project. ill be tearing into an engine either way so heck why not lol.